A little lean

[Guest]

Hey guys, I thought I'd jump in on the lean questions today. I have my new delkavic 4to1 on and it's running a little lean and overheating a bit. My carbs are gsr approved rebuilt with cycle o-rings and I have my air box with a clean k&n. It was running just slightly rich with my 4 to 2. What are y'all's suggestions? The jetting is stock. The bike runs like a beast and has 0 dead spots with very noticeable improvements in low and midrange power but I don't want to test top speed until I can make sure she' snot overheating. Do y'all think I can fix it with adjusting the mixture screws? It's only slightly popping on deceleration. How many from bottom should I start with? It's a 79' 1000

[chuck hahn]

The new pipes flow better so thats why its lean. Several things can be done to richen it a tad. First is to turn the side mixture screws IN about 1/8 turn at a time and see what the plugs look like then. Turning the mixture screws IN will take some of the air from the mix and richen the cylinder.

Next is to move the clip on the needles. Stock setting is the center groove. By moving the clip down a notch you lift the needle..which richens the flow also.

May need to open the pilot screw at the bottom a 1/4 turn to richen it up in the lower RPMs a little also.

And another method is to go up in the pilot and the main jets till shes good. Cant say which of these solutions ( or combination of them ) will fix it but these are the basic things to tweek.

[chucksuki]

thanks chuck! That's basically what I had in mind. I was hoping to get away with tweaking the mixture screws. Judging by the performance it doesn't seem I need to change jets with this setup but if I take off the air box lid I probably will. I was also thinking I might have to go down a notch on the needle. I'll warm her up and try the mixture screws and see what I get. Probably wouldn't hurt to put the carb tune on it either. I'm trying to avoid pulling the carbs until next week because I'm buying a house tomorrow and moving Friday and working all weekend. Lol when it rains it pours. How's that arm doing chuck?

[Steve]

You say it runs well at low and medium speeds, but not so well at higher speeds?

That would be a main jet change, you definitely want something larger than stock. How much larger? That depends on the header. How loud is it? The amount of noise is somewhat related to the ability to move more air (a quiter pipe is more restrictive), so a louder pipe will need larger jets. I have a relatively quiet 4-into-1 on my bike and have gone up 4 sizes on the mains. I have not yet bothered with plug readings to see if that is the right jetting, but it's not too far off.

You will not be able to adjust your general overheating situation with the mixture screws, they are most effective at idle and rather low throttle openings. They don't have much effect at anything over about 1/4 throttle.

.

[chucksuki]

No, it was pulling hard at 120mph and had plenty left in the throttle I just noticed it seems to be running a bit hotter than normal. Overall this 4 to 1 has been awesome and the bike really running great minus the bit of pop on decel and it seeming to be a bit hot. Still getting the same gas mileage as before too.

[chucksuki]

Oh, I have both baffles in the cone so it is a relatively quiet header and exhaust. My 78 750 with an old 4 into 1 (kerker?) is much louder